Growth of sexithiophene crystals on Cu(1 1 0) and Cu(1 1 0)-(2×1)O stripe phase—The influence of surface corrugation

Sexithiophene (6T) films have been grown by molecular beam deposition on two different substrates: a clean Cu(110) single crystal surface and a 1:1 Cu(110)/Cu(110)-(2×1)O stripe surface. Both substrates serve as atomically ordered two-fold symmetric templates, which induce epitaxial growth of the 6T crystallites due to surface corrugations. On both surfaces, 6T crystallizes in its low-temperature phase with (010) being the main crystallographic orientation of the 6T crystals relative to the substrate surface. Two different epitaxial growth behaviors are observed: while on the oxygen-passivated surface the long molecular axes of the 6T molecules are aligned exactly along the oxygen rows, small tilt angles relative to the densely packed copper rows are found on the clean copper surface. Classical misfit calculations seem to be insufficient to describe the observed epitaxial crystallization of sexithiophene.